Under normal operation, an integrated circuit, for example a microprocessor, generates heat that must be removed to maintain the device temperature below a critical threshold and thereby maintain reliable operation. The threshold temperature derives from many short and long term reliability failure modes and may be specified by a circuit designer as part of a normal design cycle.
The evolution of integrated circuit designs has resulted in higher operating frequency, increased numbers of transistors, and physically smaller devices. This continuing trend generates ever increasing area densities of integrated circuits and electrical connections. To date, this trend has resulted in increasing power and heat flux, in addition to increasingly non-uniform heat fluxes across the die. Further, the trend to higher power and higher, non-uniform heat flux microelectronic devices may be expected to continue into the foreseeable future, demanding continual improvement in cooling technology, at each packaging level, to prevent occurrence of thermally induced failures.
The problem of maintaining device temperature below a critical threshold value may be addressed at various levels of packaging. For example, a heat sink is a common board level component, a fan a common system level component, and a thermally conductive packaging material a common device level component. A design team may thus choose various combinations of device, board, and system level components when faced with a particular thermal challenge.